Electric Steering Wheel Position Adjustment Apparatus

ABSTRACT

The electric steering wheel position adjustment apparatus of the present invention is constructed so as to improve the support rigidity of a portion that constitutes a steering column apparatus thereof, such that the steering shaft  2   b  and the steering column  5   b  have non-expandable construction, but are able to be displaced in the axial direction; holding holes are provided in at least two locations on the top side of the column holder  31  that supports the steering column  5   b ; and in each of the holding holes, a sliding plate  35 , an elastic member  37  and a cover  38  are assembled such that the sliding plate  35  is elastically compressed by the elastic member  37  and pushes the outer circumferential surface of the steering column  5   b.

TECHNICAL FIELD

The present invention relates to an electric steering wheel positionadjustment apparatus, and more specifically to an apparatus that has anelectric motor as a drive source and that adjusts the forward-backwardposition and up-down position of a steering wheel.

BACKGROUND ART

Electric steering wheel position adjustment apparatuses having variouskinds of construction are known, and some are already being used as thesteering apparatuses of automobiles. FIG. 21 illustrates a first exampleof conventional construction that was disclosed in JP 2010-116042 (A).The steering shaft 2 to which the steering wheel 1 is fastened has acylindrical outer shaft, and a circular rod shaped inner shaft 4 that isinserted inside the outer shaft 3 so as to be able to moveback-and-forth in the axial direction, and so as to be able to transmittorque. More specifically, there is a spline fit between the middlesection to the front-end section of the inner circumferential surface ofthe outer shaft 3 and the outer circumferential surface of the rear-endsection of the inner shaft 4. The steering wheel 1 is fastened to therear-end section of the outer shaft 3.

The steering shaft 2 is inserted inside a cylindrical shaped steeringcolumn 5, and is supported so as to be able to freely rotate. Thesteering column 5 has a cylindrical outer column 6 that is supported bythe vehicle body, and a cylindrical inner column 7 that is insertedinside the outer column 6 so as to be able to move back-and-forth in theaxial direction. The portion near the rear end of the middle section ofthe outer shaft 3 is supported on the radially inside of the rear-endsection of the inner column 7 so as to be prevented from displacing inthe axial direction, and so as to be able to rotate freely. Moreover,the portion near the front end of the middle section of the inner shaft4 is supported on the radially inside of the front-end section of theouter column 6 so as to be prevented from displacement in the axialdirection, and so as to be able to rotate freely. With thisconstruction, the steering shaft 2 is supported on the inside of thesteering column 5 so as to be able to rotate freely, and the outer shaft3 and inner column 7 are capable of relative movement in theforward-backward direction with respect to the inner shaft 4 and outercolumn 6.

The apparatus of the first example of conventional construction, as anelectric actuator in order to be able to adjust the forward-backwardposition of the steering wheel 1, has: a gear housing 8 that is fastenedto the bottom surface of the outer column 6; a feed nut 9 that issupported on the inside of the gear housing 8 so as to be prevented fromdisplacement in the axial direction, and so as to be able to onlyrotate; a push-pull arm 10 that is fastened to a portion of the rear-endsection of the inner column 7 that protrudes further toward the rearthan the outer column 6; a push-pull rod 11 having a male screw section12 provided on the front half thereof that screws into the feed nut 9,and the rear-end section thereof being linked with the push-pull arm 10;and an electric motor (omitted in the figure) that is connected to thefeed nut 9 by way of a worm reducer 13, and that rotates and drives thefeed nut 9.

When adjusting the forward-backward position of the steering wheel 1,the feed nut 9 is rotated, which causes the push-pull rod 11 to bedisplaced in the axial direction. Due to this displacement, the innercolumn 7, by way of the push-pull arm 10, is displaced in the samedirection as the push-pull rod 11, and by causing the outer shaft 3 thatis supported on the inside of the inner column 7 to move in theforward-backward direction together with the inner column, theforward-backward position of the steering wheel 1 is adjusted.

In the electric steering wheel position adjustment apparatus of thisfirst example of conventional construction, there is a possibility thatthe driver that operates the steering wheel 1 will experience anunpleasant or uncomfortable feeling due to a small space that exist inthe area of fit between the rear-end section of the outer column 6 andthe front-end section of the inner column 7. In other words, in theelectric steering wheel position adjustment apparatus, differing from amanual apparatus, even in the state in which the adjusted position ofthe steering wheel 1 is maintained, the diameter of the rear-end sectionof the outer column 6 is not reduced, and a small space remains in thearea of fit. Due to this small space, there is a possibility that theinner column 7 that supports the outer shaft 3 to which the steeringwheel 1 is fastened will be loose with respect to the outer column 6that is supported by the vehicle body. Due to this loose fit, thefeeling of support rigidity of the steering wheel 1 will decrease, andthere is a possibility that the driver that operates the steering wheel1 will experience an unpleasant feeling. Moreover, this looseness causesthe resonant frequency of the members of the electric steering wheelposition adjustment apparatus that constitutes the steering columnapparatus that includes the steering shaft 2 and steering column 5 todecrease, and when there is small vibration of the vehicle body whentraveling over a bad road or the like, there is a possibility thatunpleasant noise or vibration will occur in this steering columnapparatus.

FIG. 22 and FIG. 23 illustrate a second example of conventionalconstruction that is disclosed in JP 2006-297989 (A). In this secondexample of conventional construction as well, as in the first example ofconventional construction, the steering shaft 2 a is supported on theinside of the steering column 5 a so as to be able to rotate freely, andthe outer shaft 3 a and inner column 7 a are able move in theforward-backward direction relative to the inner shaft 4 a and outercolumn 6 a.

In this second example of conventional construction, by using a linearmotion ultrasonic motor 15 that is supported by the bottom-end sectionof an installation bracket 14 as an actuator in order to be able toadjust the forward-backward position of the steering wheel 1, it ispossible for the inner column 7 a to be displaced in the axial directionwith respect to the outer column 6 a. More specifically, a moving piece16 of the linear motion ultrasonic motor 15 and inner column 7 a arelinked by a transmission member 17, and by transmitting the movement ofthe moving piece 16 to the inner column 7 a, it is possible to move theinner column 7 a in the forward-backward direction. The base-end sectionof the transmission member 17 is fastened by screws to the inner column7 a, and the tip-end section of the transmission member 17 is linked tothe moving piece 16 by way of a spherical joint 18. The spherical joint18 has: an engaging concave section 19 that is formed in the movingpiece 16; a spacer 20 that fits with and is supported by the engagingconcave section 19, and that has an inner circumferential surface thatis a spherical concave surface; and a spherical surface engaging section21 that engages with the inner circumferential surface of the spacer 20.

When adjusting the forward-backward position of the steering wheel 1,the linear motion ultrasonic motor 15 causes the moving piece 16 to bedisplaced in the axial direction of the steering column 5 a. Thisdisplacement, by way of the transmission member 17, causes the innercolumn 7 a to be displaced in the same direction as the moving piece 16,which causes the outer shaft 3 a that is supported on the inside of theinner column 7 a to move in the forward-backward direction together withthe inner column 7 a. As a result, as illustrated by the two-dot chainline in FIG. 22, it becomes possible to adjust the forward-backwardposition of the steering wheel 1.

In the case of the construction of this second example of conventionaltechnology, there is a problem in that due to the construction of theengagement area between the moving piece 16 and the transmission member17, the manufacturing cost for maintaining smooth operation increases.In other words, in order to smoothly perform adjustment of theforward-backward position of the steering wheel 1 without any looseness,it is necessary to properly regulate the fitting strength at theengagement area between the spherical engaging section 21 of thetransmission member 17 and the spacer 20. When the fitting strength isto low, a positive gap occurs in this engagement area, and loosenessoccurs between the spherical engaging section 21 and the spacer 20,which easily causes rattling of the steering wheel 1 in theforward-backward direction. On the other hand, when the fitting strengthis too high, pivotal displacement of the spacer 20 with respect to thespherical engaging section 21 cannot be performed smoothly.

In the construction of this second example of conventional technology,the amount of movement in the forward-backward direction of the movingpiece 16 is large, and unless there is a good degree of parallelaccuracy between the movement direction of this moving piece 16 and themovement direction of the inner column 7 a when performingforward-backward position adjustment of the steering wheel 1, as theforward-backward position of the steering wheel 1 is adjusted, thetransmission member 17 will be displaced in the axial direction of thetransmission member relative to the moving piece 16. This relativedisplacement causes rubbing in the axial direction of the transmissionmember 17 between the outer circumferential surface of the spacer 20 andthe inner circumferential surface of the engaging concave section 19. Inthis case, when the fitting strength is too high, and pivotaldisplacement of the spacer 20 with respect to the spherical engagingsection 21 is not performed smoothly, there will be strong rubbingbetween the outer circumferential surface of the spacer 20 and the innercircumferential surface of the engaging concave section 19, and there isa possibility that noise or vibration will occur, causing the passengersin the automobile to experience an uncomfortable feeling. Particularly,in this state, the surface that allows relative displacement in theaxial direction of the transmission member 17 between the transmissionmember 17 and the moving piece 16 is limited to only one locationbetween the outer circumferential surface of the spacer 20 and the innercircumferential surface of the engaging concave section 19, so therubbing length easily becomes long, which makes it even easier for noiseand vibration to occur.

Performing high precision processing of the inner circumferentialsurface of the spacer 20, which is a spherical concave surface, and theouter circumferential surface of the spherical engaging section 21,which is a spherical convex section, in order to prevent the occurrenceof noise and vibration is connected to higher costs. Moreover, whenmanufacturing the spherical engaging section 21 with high precision, itis not possible to avoid the outer diameter of the transmission member17 becoming small on the base-end section of the spherical engagingsection 21. It is easy for large stresses to occur in the neck sectionof this transmission member 17 during adjustment of the forward-backwardposition of the steering wheel 1, and so such construction as this isnot advantageous from the aspect of maintaining sufficient durabilitywhen used over a long period of time.

As construction for preventing the occurrence of noise and vibration inthe portion of the steering column apparatus, JP 5,076,908 (B2), forexample, discloses a mechanism as illustrated in FIG. 24 in whichholding holes 22 are provided in part in the axial direction of theouter column 6 b, and adjustment screws 24 that are screwed into femalethreads 23 that are formed in the holding holes 22 press synthetic resinpads 26 that come in contact with the outer circumferential surface ofthe inner column 7 b by way of disc springs 25, which prevents loosenessof the portion that constitutes the steering column apparatus. However,in this mechanism, when the force by which the pads 26 press against theouter circumferential surface of the inner column 7 b is made largeenough to be able to prevent looseness, the drive load on the electricmotor increases, and there is a problem in that the operation noisebecomes large.

RELATED LITERATURE Patent Literature

-   [Patent Literature 1] JP 2010-116042 (A)-   [Patent Literature 2] JP 2006-297989 (A)-   [Patent Literature 3] JP 5,076,908 (B2)-   [Patent Literature 4] JP H09-323658 (A)-   [Patent Literature 5] JP H10-119793 (A)-   [Patent Literature 6] JP 2005-255040 (A)-   [Patent Literature 7] JP 2009-006743 (A)-   [Patent Literature 8] JP 2010-116042 (A)-   [Patent Literature 9] DE 10251764 (A1)

SUMMARY OF INVENTION Problem to be Solved by Invention

The object of the present invention is to provide at low costconstruction of an electric steering wheel position adjustment apparatusthat improves the rigidity of the portion that constitutes the steeringcolumn apparatus, so that the driver operating the steering wheel doesnot experience an unpleasant feeling, and that is capable of performingposition adjustment of the steering wheel stably and smoothly.

Means for Solving Problems

The electric steering wheel position adjustment apparatus of the presentinvention has:

a steering shaft that has a rear-end section which a steering wheel issupported by and fastened to;

a column unit that extends in the axial direction of the steering shaft,that rotatably supports the steering shaft on the inside thereof, andthat has:

-   -   a support section supported by a portion that is fastened to a        vehicle body or to a vehicle body-side bracket that is supported        by the portion that is fastened to the vehicle body, the support        section not being displaced during position adjustment of the        steering wheel; and    -   an adjusted section supported by the support section so as to be        displaceable in the axial direction of the steering shaft        together with at least part of the steering shaft during        position adjustment of the steering wheel;

an electric actuator that is fastened to the bottom side of the supportsection, that has an electric motor as the drive source, and that causesthe adjusted section to be displaced in the axial direction with respectto the support section; and

mechanisms that push the adjusted section downward, and that areprovided in at least two locations on the top side of the supportsection that are separated in the forward-backward direction of thecolumn unit.

In the apparatus of the present invention, preferably a pair ofpreloaded angular ball bearings having back-to-back contact angles arelocated between both end sections in the forward-backward direction ofthe adjusted section and at least part of the steering shaft, and thepair of ball bearings rotatably support the at least part of thesteering shaft with respect to the adjusted section in a state thatdisplacement in the axial direction of the steering shaft with respectto the adjusted section is prevented.

Preferably, the both end sections in the forward-backward direction ofthe adjusted section are constructed by reduced-diameter sections havingdiameters that are smaller than the diameter of the middle section inthe forward-backward direction of the adjusted section,

the middle section in the forward-backward direction of the adjustedsection is constructed by a middle cylindrical section having an outerdiameter that does not change in the axial direction of the adjustedsection,

the pair of ball bearings are located between the inner circumferentialsurfaces of the both end sections in the forward-backward direction ofthe adjusted section and the outer circumferential surface of the atleast part of the steering shaft, and

the mechanisms that push the adjusted section downward are provided onthe support section so as not to separate from the middle cylindricalsection regardless of displacement of the adjusted section in the axialdirection with respect to the support section.

Preferably, in the apparatus of the present invention, each of themechanisms that push the adjusted section downward has:

a holding hole that is formed so as to pass through between orcommunicate the inner circumferential surface and the outercircumferential surface of the support section;

a sliding plate;

an elastic member; and

a cover.

the sliding plate, the elastic member and the cover being assembled inthe holding hole in order from the inside in the radial direction of thesupport section, and

the elastic member is elastically compressed between the sliding plateand the cover such that the sliding plate pushes the outercircumferential surface of the adjusted section.

Preferably the spacing in the axial direction of the mechanisms thatpush the adjusted section downward is essentially equal to the maximumrange of movement of the adjusted section in the axial direction of thesupport section.

Preferably, the electric actuator has:

a forward-backward feed screw rod that is arranged parallel with theadjusted section and that is rotated and driven by the electric motor;

a moving piece that is screwed onto the forward-backward feed screw rodand that moves in the forward-backward direction according to therotation of the forward-backward feed screw rod; and

a transmission member, the tip-end section thereof being connected tothe moving piece, and the base-end section thereof being joined to themiddle cylindrical section of the adjusted section, and that transmitsthe movement of the moving piece to the adjusted section.

In this case, preferably an engaging concave section is provided in themoving piece; the tip-end section of the transmission member engageswith the engaging concave section of the moving piece by way of aspacer; the engaging concave section of the moving piece has an innercircumferential surface that is a cylindrical concave surface having aninner diameter that does not change in the axial direction of thetransmission member; the tip-end section of the transmission member hasan outer circumferential surface that is a cylindrical convex surfacehaving an outer diameter that does not change in the axial direction ofthe transmission member; and the spacer has an outer circumferentialsurface that is a cylindrical convex surface having an outer diameterthat does not change in the axial direction of the transmission memberand an inner circumferential surface that is a cylindrical concavesurface having an inner diameter that does not change in the axialdirection of the transmission member.

The present invention is particularly and suitably applied to anelectric steering wheel position adjustment apparatus, in which thesteering shaft, has integrated construction of which the overall lengthdoes not expand or contract, and the adjusted section has a steeringcolumn having integrated construction of which the overall length doesnot expand or contract; and further has:

an expandable intermediate shaft that transmits the rotation of thesteering shaft to an input shaft of a steering gear unit; and

a universal joint that connects the front-end section of the steeringshaft, and the rear-end section of the intermediate shaft, and

the electric actuator causes the steering column to be displaced in theaxial direction of the steering column, causing the steering shaft tomove in the forward-backward direction, and the movement of the steeringshaft is compensated by causing the intermediate shaft to expand orcontract.

However, the present invention can also be applied to construction inwhich a steering shaft has an inner shaft, and an outer shaft, whichconstitutes the at least part of the steering shaft, and that fitsaround the inner shaft so as to be able to slide in the axial directionof the steering shaft, and so as to be able to transmit torque to theinner shaft; the support section has an outer column; the adjustedsection has an inner column that fits inside the outer column so as tobe able to slide in the axial direction of the adjusted section, thefront-end section of the inner shaft is connected to an intermediateshaft by way of a universal joint; the steering wheel is supported byand fastened to the rear-end section of the outer shaft; and the outershaft displaces in the forward-backward direction together with theinner column during adjustment of the forward-backward position of thesteering wheel.

Effect of the Invention

With the present invention, an electric steering wheel forward-backwardposition adjustment apparatus is provided that improves the supportrigidity of the steering column apparatus area thereof, and makes itpossible to perform steering wheel position adjustment smoothly withoutthe driver experiencing an uncomfortable or unpleasant feeling.

In other words, mechanisms that elastically push a portion (adjustedsection) of a column unit of the steering column apparatus that isdisplaced in the forward-backward direction together with at least partof the steering shaft downward with respect to the structure (supportsection) that supports the portion are provided in at least twolocations on the top side of the support section that are separated inthe forward-backward direction, so it is possible to suppress loosenessbetween these members; and in the steering column apparatus, it ispossible to improve the support rigidity in the area of fit of theadjusted section and the support section.

Particularly, by constructing both the steering shaft and steeringcolumn with non-expandable integrated construction, the rigidity of thesteering shaft and steering column of the steering column apparatus ismaintained, and thus the support rigidity of the steering columnapparatus is further achieved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a vertical cross-sectional side view illustrating a firstexample of an embodiment of the present invention.

FIG. 2 is an enlarged view of the right half in FIG. 1.

FIG. 3 is an enlarged view of part A in FIG. 2.

FIG. 4 is an enlarged view of part B in FIG. 2.

FIG. 5 is an enlarged view of part C in FIG. 2.

FIG. 6 is a perspective view illustrating the first example as seen fromabove in the front.

FIG. 7 is an enlarged view of the right half in FIG. 6.

FIG. 8 is a perspective view that illustrates the first example as seenfrom above on the opposite side from FIG. 7.

FIG. 9 is a perspective view that illustrates the right half in FIG. 6as seen from below.

FIG. 10 is a partial cross-sectional drawing that illustrates the firstexample as seen from the right in FIG. 1 and FIG. 2.

FIG. 11 is a partial cross-sectional drawing that illustrates the firstexample as seen from the left in FIG. 1.

FIG. 12 is a top view illustrating the first example as seen from abovein FIG. 2.

FIG. 13 is a bottom view illustrating the first example as seen frombelow in FIG. 2.

FIG. 14 is an enlarged cross-sectional drawing of section D-D in FIG. 2.

FIG. 15 is an enlarged cross-sectional drawing of section E-E in FIG. 2.

FIG. 16 is a partial enlarged cross-sectional drawing of the supportsection of both the front and rear ends of a screw rod forforward-backward position adjustment as seen from the same direction asin FIG. 1 and FIG. 2.

FIG. 17 is a partial enlarged cross-sectional drawing of the supportsection of both the top and bottom ends of a screw rod for up-downposition adjustment as seen from the same direction as in FIG. 1 andFIG. 2.

FIG. 18 is a schematic drawing for explaining the change of the amountof expansion and contraction of the intermediate shaft when adjustingthe up-down position of the steering wheel according to theforward-backward position of the steering wheel.

FIG. 19 is a vertical cross-sectional side view illustrating a secondexample of an embodiment of the present invention.

FIG. 20 is an enlarged view of part F in FIG. 19.

FIG. 21 is a partial vertical cross-sectional side view illustrating afirst example of conventional construction.

FIG. 22 is a vertical cross-sectional side view illustrating a secondexample of conventional construction.

FIG. 23 is an enlarged view of part G in FIG. 22.

FIG. 24 is a partial cross-sectional drawing illustrating a conventionalgap adjustment mechanism for adjusting the gap between the outer columnand inner column that can be applied to the first example and secondexample of conventional construction.

MODES FOR CARRYING OUT INVENTION First Example

FIG. 1 to FIG. 18 illustrate a first example of an embodiment of thepresent invention. The electric steering wheel position adjustmentapparatus of this example has a steering shaft 2 b and a cylindricalsteering column 5 b, neither of which is expandable or contractible, ina section thereof that functions as a steering column apparatus. In theconstruction of this example, the forward-backward position and up-downposition of the steering wheel (see FIG. 21) that is supported by andfastened to the rear-end section of the steering shaft 2 b thatprotrudes from the opening on the rear end of the steering column 5 bcan each be adjusted within a specified range, however, forward-backwardposition adjustment of the steering wheel 1 is achieved by moving theoverall steering shaft 2 b and steering column 5 b in the axialdirection. Therefore, in this example, the overall steering column 5 bcorresponds to an adjusted section of the column unit of the presentinvention.

In the construction of this example, the overall length of the steeringshaft 2 b does not expand or contract, however the steering shaft 2 b isable to move in the axial direction (forward-backward direction) of thesteering shaft, so as illustrated in FIG. 1 and FIG. 6, as anintermediate shaft 28 that is linked to the front-end section of thesteering shaft 2 b by way of a universal joint 27 a so as to be able totransmit torque, construction is employed in which the end sections ofan intermediate inner shaft 29 and intermediate outer shaft 30 fittogether using a spline fit such that torque can be transmitted and theoverall length can be expanded and contracted. In other words, byexpanding or contracting the intermediate shaft 28, movement in theforward-backward direction of the steering shaft 2 b is compensated for.The front-end section of the intermediate shaft 28 is linked to an inputshaft (omitted in the figure) of a steering gear unit for applying asteering angle to the steered wheels (front wheels) by way of anotheruniversal joint 27 b.

In the construction of this example, the installation position of theuniversal joint 27 a that links the front-end section of the steeringshaft 2 b and the rear-end section of the intermediate shaft 28 isappropriately regulated such that during position adjustment of thesteering wheel 1, the amount of relative displacement between thesteering shaft 2 b and the intermediate shaft 28 is kept to minimum, andsuch that the position adjustment of the steering wheel 1 can beperformed smoothly. More specifically, in order support a column holder31 that holds the steering column 5 b so as to be able to be pivotallydisplaced with respect to a vehicle body-side bracket 32, a pair of leftand right tilt shafts 33 (see FIG. 9 and FIG. 11) that are concentricwith each other and the steering shaft. 2 b are located in positionssuch that the center axes of each are orthogonal with each other.Furthermore, as illustrated in FIG. 3, the center axis O_(C) of the pairof tilt shafts 33 is located in the center position in theforward-backward direction between the center position O_(F) ofdisplacement on the front-end side of the universal joint 27 a and thecenter position O_(B) of displacement on the rear-end side.

The center position O_(F) of displacement on the front-end side is thecenter position of displacement of the universal joint. 27 a, or inother words, the center point position of the joint cross 34 of theuniversal joint 27 a, in a state in which the steering wheel 1 isdisplaced to the front-end position of the adjustable range. The centerposition O_(B) of displacement on the rear-end side is the centerposition of displacement of the universal joint 27 a in a state in whichthe steering wheel 1 is displaced to the rear-end position of theadjustable range. In this example, the center axis O_(C) of the pair oftilt shafts 33 is located in the center position of the line segmentthat connects the center position O_(F) of displacement on the front-endside and the center position O_(B) of displacement on the rear-end side.Therefore, when the length of the line segment that connects the centerposition O_(F) of displacement on the front-end side and the centerposition O_(B) of displacement on the rear-end side is taken to be L,the distances between the center axis O_(C) of the pair of tilt shafts33 and the center position O_(F) of displacement on the front-end sideand the center position Os of displacement on the rear-end side are eachL/2. However, even when the center axis O_(C) of the pair of tilt shafts33 is shifted by ±L/10, or preferably by ±L/20, from the position in thefigure, the center axis O_(C) of the pair of tilt shafts 33 is locatedin nearly the center position between the center position O_(F) ofdisplacement on the front-end side and the center position O_(B) ofdisplacement on the rear-end side, so there is no particular problem.

The column holder 31 that holds the steering column 5 b so thatdisplacement of the steering column 5 a in the axial direction(forward-backward direction) is possible is formed into a hollow bodyshape, or more specifically, a substantially cylindrical shape by diecasting a light metal alloy, for example. The column holder 31corresponds to a support section that constitutes the section of thesteering column apparatus of the present invention. In order toeliminate looseness of the steering column 5 b with respect to thecolumn holder 31, holding holes 22 a are formed in two locations thatare separated in the forward-backward direction on the tip surface ofthe column holder 31 so as to pass through between the innercircumferential surface and outer circumferential surface of the columnholder 31. As illustrated in FIG. 4 and FIG. 14, a sliding plate 35, awasher 36 and a disc spring 37 are installed on the inside of the eachof the holding holes 22 a, and the opening section on the top end ofeach holding hole 22 a is covered by a screw cover 38. The sliding plate35 is made of a high polymer material such as a synthetic resin likepolyacetal (POM) or a synthetic rubber having excellent slidingproperties. In this state, the sliding plates 35 that are located in theend section on the radially inside of the holding holes 22 a are pressedagainst the outer circumferential surface (top surface) of the steeringcolumn 5 b by the elastic force of the disc springs 37, so that thesteering column 5 b is not loose inside the column holder 31. Thespacing in the axial direction of the mechanisms for preventinglooseness of the steering column 5 b is arbitrary, however, in thisexample, the spacing in the axial direction of the mechanisms isessentially the same as the maximum movable range in the axial directionof the steering unit.

In this example, from the aspect of maintaining the required rigidity,the steering column 5 b is integrally formed into a hollow body shapeusing an extruded pipe or seam welded pipe made of an aluminum alloy oriron-based alloy. However, it is also possible to employ construction inwhich plural elements are combined by welding or fitting. In thisexample, the steering column 5 b has a substantially cylindrical shape,but is not limited to this. By performing a drawing process on both endsections in the forward-backward direction of the steering column 5 b,reduced-diameter sections 39 a, 39 b having outer diameters that aresmaller than the outer diameter of the middle section in theforward-backward direction are formed. Moreover, the middle section inthe forward-backward direction of the steering column 5 b is taken to bea middle cylindrical section 40 having an outer diameter that does notchange in the axial direction, and both end sections in theforward-backward direction of this middle cylindrical section 40 arecontinuous with the reduced-diameter sections 39 a, 39 b by inclinedsurface sections 41 a, 41 b. The length in the axial direction of themiddle cylindrical section 40 and the installation positions of theholding holes 22 a are regulated by the relationship with the amount ofadjustment in the forward-backward direction of the steering wheel 1,and the sliding plates 35 do not separate from the middle cylindricalsection 40 regardless of the displacement in the axial direction of thesteering column 5 b with respect to the column holder 31.

The steering shaft 2 b is integrally formed into a cylindrical shape orcircular rod shape using drawn pipe or seam welded pipe made of aniron-based alloy, or an extruded pipe or drawn pipe made of an aluminumalloy, however, as in the case of the steering column 5 b, it is alsopossible to employ construction in which plural elements are combined bywelding or fitting. The steering shaft 2 b is supported on the radiallyinside of the steering column 5 b by a pair of ball bearings 42 a, 42 bthat are located on both end sections in the forward-backward directionin a state such that displacement in the axial direction with respect tothe steering column 5 b is prevented.

A pair of angular ball bearings 42 a, 42 b that have back-to-backcontact angles and that are preloaded, are located between the innercircumferential surface of the reduced-diameter sections 39 a, 39 b, andthe outer circumferential surface of the portions near both ends of themiddle section of the steering shaft 2 b. Therefore, in this example, asillustrated in FIG. 4, the outer rings 43 a, 43 b of the pair of ballbearings 42 a, 42 b are fastened around the edge sections on theopenings of the reduced-diameter sections 39 a, 39 b in a state suchthat displacement in a direction toward each other is prevented.Moreover, the inner ring 44 a of the ball bearing 42 a on the front sideis fastened around the portion near the front end of the middle sectionof the steering shaft 2 b by a retaining ring 45 that is fastened aroundthe steering shaft 2 b so that displacement in the forward direction isprevented. On the other hand, the inner ring 44 b of the ball bearing 42b on the rear side is fastened around the steering shaft 2 b with aloose fit by a push nut 46 in a state such that displacement in thebackward direction is prevented. An elastic member 47 such as a discspring is held between the surface on the front side of the push nut 46and the rear-end surface of the inner ring 44 b, and this elastic member47 applies an elastic force on the inner ring 44 b in the forwarddirection. With this kind of construction, the steering shaft 2 b issupported on the radially inside of the steering column 5 b in a statesuch that displacement in the axial direction is prevented, and so as tobe able to rotate freely with no looseness.

In this example, back-to-back angular ball bearings instead ofdeep-groove ball bearings are used as the pair of ball bearings 42 a, 42b, and are installed in a state being preloaded from the axial directionof the steering shaft 2 b. Therefore, the preloading makes it possibleto prevent looseness of the bearings, and it is possible to reduce therotation torque of the bearings, so a steering apparatus having goodsteering stability of the steering wheel 1 is achieved. Moreover, a pushnut 46 is used for fastening the inner ring 44 b on the rear side, sothere is no need to form a fastening groove on the rear-end section ofthe steering shaft 2 b where it is easy for large forces to be appliedfrom the steering wheel 1. Therefore, it is possible to maintain thestrength and rigidity of the rear-end section of the steering shaft 2 bwithout having to increase the thickness of the steering shaft 2 b. Ascrew hole 48 is provided on the rear-end section of the steering shaft2 b, and by using this screw hole 48, the steering wheel 1 is fastenedto and supported by the steering shaft 2 b, and the diameter of therear-end section of the steering shaft 2 b is sufficiently maintained.

As illustrated in FIG. 9 and FIG. 11, the column holder 31 is supportedby the vehicle body-side bracket. 32 by the pair of tilt shafts 33 thatare provided on both sides of the front-end section of the column holderso as to be concentric with each other, and the column holder 31 is ableto be pivotally displaced around these tilt shafts 33. The vehiclebody-side bracket 32 is integrally formed by die cast molding of a lightmetal alloy for example, and is supported by a portion that is fastenedto the vehicle body so that displacement in the forward direction due toan impact load that is applied during a secondary collision is possible.In order for this, a pair of left and right installation plate sections49 are provided on the vehicle body-side bracket 32, long holes 50 thatextend in the forward-backward direction are formed in the frontsections of the installation plate sections 49, and notches 51 that areopen on the rear-end edges of the installation plate sections 49 areformed in the rear-end sections. Sliding plates 52 a, 52 b are fastenedto each of the long holes 50 and notches 51, and by the way of bolts orstuds that are inserted in through holes in these sliding plates 52 a,52 b, the pair of installation plate sections 49 are fastened to andsupported by a portion that is fastened to the vehicle body. In thisstate, the vehicle body-side bracket 32 is always firmly supported by aportion that is fastened to the vehicle body, however, when a largeimpact load is applied in the forward direction during a secondarycollision, the vehicle body-side bracket 32 is displaced in the forwarddirection within the range that the bolts or studs are able to bedisplaced inside the long holes 50.

An actuator case 53 that is manufactured separately from the steeringcolumn 5 b is joined and fastened to a portion of the column holder 31that is on the bottom side of the steering column 5 b using pluralbolts.

As illustrated in FIG. 2 and FIG. 5, a forward-backward feed screwapparatus 54 and an up-down feed screw apparatus 55 that constitute anelectric actuator are provided inside the actuator case 53. In thisexample, a forward-backward position adjustment actuator is formed bythe forward-backward feed screw apparatus 54 and a forward-backwardelectric drive motor 56. The forward-backward feed screw apparatus 54,with the forward-backward electric drive motor 56 as a drive source,causes the steering column 5 b to be displaced in the forward-backwarddirection, and has a forward-backward feed screw rod 58 that is arrangedparallel with the steering column 5 b, and a moving piece 16 a that hasa forward-backward feed nut that screws onto the forward-backward feedscrew rod 58. As illustrated in FIG. 5 and FIG. 16, both the front andrear end sections of the forward-backward feed screw rod 58 aresupported by the actuator case 53 by way of a pair of ball bearings 59a, 59 b such that displacement in the axial direction is prevented, sothat only rotation is possible. The forward-backward feed screw rod 58is connected to the forward-backward electric drive motor 56 by way of aworm reducer, and is rotated and driven by the forward-backward electricdrive motor 56. In this example, a forward-backward feed screw apparatus54 that has the forward-backward electric drive motor 56 as a drivesource is used, however, instead of this, it is also possible to use alinear motor that has a brake function, such as a linear motionultrasonic motor.

The moving piece (forward-backward feed nut) 16 a has a base section 60and a connecting section 61 that is provided above the base section 60.A screw hole 62 that screws onto the forward-backward feed screw rod 58is formed on the base section 60. The connecting section 61 and thesteering column 5 b are connected by way of a transmission member 17 aso as to be able to transmit force in the forward-backward directiontherebetween. The transmission member 17 a is formed by performing coldforging on raw material made of an iron-based alloy such as carbon steelor stainless steel, and a male screw section 63 is provided on thebase-end section (top-end section), an outward-facing flange section 64is provided on the middle section, and a circular column section 65 isprovided on the tip-end section (bottom-end section). A fastening hole66 such as a hexagonal hole is formed in the tip-end surface (bottom-endsurface) of the circular column section 65 so that the tip-end sectionof a tool such as a hexagonal wrench can be fastened. In thetransmission member 17 a of this example, there is no neck section wherethe outer diameter becomes particularly small.

As illustrated in FIG. 5 and FIG. 14, the transmission member 17 a isfastened with screws to the bottom surface of the middle cylindricalsection 40 of the steering column 5 b so that tilting in theforward-backward direction is sufficiently suppressed. Morespecifically, with a cylindrical section of a nut plate 68 inserted intoa though hole 67 that is formed on the bottom surface of the middlecylindrical section 40 of the steering column 5 b, the nut plate 68 isfastened to the circumferential edge section of the through hole 67 bycrimping so as to be mounted to the steering column 5 b from the innercircumferential surface side thereof. A radially inward side spacer 69having an outer diameter that is smaller than the outer diameter of theflange section 64 is placed on the top surface of the flange section 64,and an radially outward side spacer 70 is mounted around this radiallyinward side spacer 69. The radially inward side spacer 69 is made of ahard material such as an iron-based alloy. However, the radially outwardside spacer 70 is made of a high polymer material such as syntheticresin, hard rubber, hard vinyl or the like, or a material having aspecified hardness but also having large internal loss and a vibrationabsorbing capability such as a soft metal. With the bottom surface nearthe radially inside of the radially outward side spacer 70 in contactwith the top surface of the portion near the radially outside of theflange section 64, the top surface of the radially inward side spacer 69and the top surface of the radially outward side spacer 70 are locatedon the same plane. Furthermore, a filler piece 71 is held between thetop surfaces of the radially inward side spacer 69 and the radiallyoutward side spacer 70 and the bottom surface (outer circumferentialsurface of the bottom-end section) of the steering column 5 b. Thefiller piece 71 is made of a hard material such as an iron-based alloyand is formed into a circular ring shape or frame shape as a whole witha wedge shaped cross sectional shape. By screwing the male screw section63 that is provided on the top-end section of the transmission member 17a into the nut plate 68 and further tightening, the transmission member17 a is firmly supported by and fastened to the bottom surface of themiddle section of the steering column 5 b. The transmission member 17 ais supported by and fastened to the middle cylindrical section 40 of thesteering column 5 b having a relatively large outer diameter, so thetransmission member 17 a does not hinder the rotation of the steeringshaft 2 b. Moreover, by combining the radially outward side spacer 70with the radially inward side spacer 69 made of a hard material, theradially outward side spacer 70 will not be exhausted. Furthermore, evenin the case where the radially outward side spacer 70 drops down fromthe flange section 64 and comes in contact with the moving piece 16 a,the occurrence of noise is suppressed since the material of the radiallyoutward side spacer 70 is not hard.

The transmission member 17 a that is supported by and fastened to thebottom surface of the middle cylindrical section 40 of the steeringcolumn 5 b and the moving piece 16 a that is screwed onto theforward-backward feed screw rod 58 are combined so as to be able totransmit movement in the forward-backward direction, and so as to beable to be displaced relative to each other in the axial direction ofthe transmission member 17 a. More specifically, an engaging concavesection 19 a that opens upward is provided in the center section of theconnecting section 61 of the moving piece 16 a, and the circular columnsection 65 of the transmission member 17 a is inserted into thisengaging concave section 19 a. A cylindrical shaped spacer 72 is placedbetween the inner circumferential surface of the engaging concavesection 19 a and the outer circumferential surface of the circularcolumn section 65 so that there is no looseness, and so that slidingmovement in the axial direction of the circular column section 65 ispossible. The inner circumferential surface and the outercircumferential surface of the cylindrical spacer 72, except for chamfersections on both ends in the axial direction, are cylindrical surfaceshaving no change in the diameter in the axial direction.

In a state that the transmission member 17 a and the moving piece 16 aare combined, the moving piece 16 a does not rotate with respect to theforward-backward feed screw rod 58. When the forward-backward feed screwrod 58 is rotated by the forward-backward electric drive motor 56, themoving piece 16 a moves along the forward-backward feed screw rod 58 ina direction that corresponds to the direction of rotation. The directionof movement of the moving piece 16 a is basically in the direction ofthe center axis of the column holder 31, and is parallel to thedirection of movement of the steering column 5 b. However, due tomanufacturing error or assembly error of a product, the direction of themovement of the moving piece 16 a and the direction of movement of thesteering column 5 b may be a little nonparallel. For example, in casethat the direction of the abutting section (contact surfaces) betweenthe bottom surface of the column holder 31 and the top surface of theactuator case 53 does not match the direction of movement of the movingpiece 16 a or the direction of movement of the steering column 5 b,these directions of movement may be a little nonparallel. In that case,the transmission member 17 a is displaced in the axial direction of thetransmission member 17 relative to the moving piece 16 a. This relativedisplacement is performed while there is slippage at the area of contactbetween the inner circumferential surface of the cylindrical spacer 72and the outer circumferential surface of the circular column section 65,and at the area of contact between the outer circumferential surface ofthe cylindrical spacer 72 and the inner circumferential surface of theengaging concave section 19 a. These circumferential surfaces are simplecylindrical surfaces, so the surfaces can be processed with highprecision without a large increase in cost, and because the slidingsections of these members are located at two locations, the relativedisplacement between these members can be performed smoothly. In orderthat the transmission member 17 a can be displaced in theforward-backward direction, a long hole 89 in the forward-backwarddirection that extends in the axial direction of the column holder 31 isprovided in part of the column holder 31.

In this example, an up-down feed screw apparatus 55 and up-down electricdrive motor 57 are provided as an electric actuator for up-down positionadjustment. With the up-down electric drive motor 57 as a drive source,the up-down feed screw apparatus 55 causes the rear section of thesteering column 5 b to be displaced (raise or lower) in the up-downdirection. In this example, the up-down feed screw apparatus 55 causesthe entire column holder 31 to be pivotally displaced with respect tothe vehicle body-side bracket, with the pair of tilt shafts 33 as thecenter of rotation. More specifically, as illustrated in FIG. 8 to FIG.10, a U-shaped support frame 73 is provided at the rear-end section ofthe vehicle body-side bracket 32, and the rear-end section of the columnholder 31 is held inside this support frame 73 so as to be able to raiseor lower without looseness. The support frame 73 has inside surfacesthat are parallel with each other. On the other hand, convex sections 74a, 74 b that have outside surfaces that are parallel with each other areprovided on both the right and left sides of the rear-end section of thecolumn holder 31 so as to protrude out in the width direction. Theoutside surfaces of the convex sections 74 a, 74 b and the insidesurfaces of the support frame 73 engage by way of respective slidingplates 75 a, 75 b. One sliding plate 75 a is thicker than the othersliding plate 75 b, and by pressing this thick sliding plate 75 a towardthe other sliding plate 75 b using a pressure screw 76, loosenessbetween the support frame 73 and the column holder 31 is eliminated. Thepressure screw 76, after being tightened to a specified torque, isprevented from coming loose by a lock nut. In this example, an up-downfeed screw apparatus 55 having the up-down electric drive motor 57 as adrive source is used, however, instead of this, it is also possible touse a linear motor having a brake function such as a linear motionultrasonic motor.

As illustrated in FIG. 5 and FIG. 15, by combining the engaging hole 77that is provided in the center section in the width direction of thesupport frame 71 and the up-down feed screw apparatus 55, the rear-endsection of the column holder 31 is able to move up or down (raise orlower) according to the power flowing to the up-down electric drivemotor 57. As illustrated in FIG. 5 and FIG. 17, both the top and bottomend section of the up-down feed screw rod 78 of the up-down feed screwapparatus 55 is supported by the actuator case 53 by way of a pair ofball bearings 79 a, 79 b such that only rotation is possible. Theup-down feed screw rod 78 is connected to the up-down electric feeddrive motor 57 by way of a worm reducer, and is rotated and driven bythe up-down electric drive motor 57.

An up-down feed nut 80 screws around the middle section of the up-downfeed screw rod 78. The up-down feed nut 80 is formed into a incompletecircular ring shape using a metal material such as an iron-based metalhaving elasticity, and by adjusting the interference of the screwengagement section with the up-down feed screw rod 78 with a screw 81,it is possible to eliminate any looseness in the screw engagementsection. Moreover, the tip-end section of an engaging arm 82 that isintegrally provided on the up-down feed nut 80 and the engaging hole 77can be joined by way of a spherical joint 83 so as to be able totransmit force in the up-down direction and so as to be able to bepivotally displaced. The spherical joint 83 is formed on the tip-endsection of the engaging arm 82, and has a spherical engaging section 84having an outer circumferential surface that is a partial sphericalconvex surface, and a spacer 85 that is formed into a cylindrical shapeusing a material such as synthetic resin that slides easily, and has aninner circumferential surface that is a partial spherical concavesurface. A screw hole is formed in the center section of the sphericalengaging section 84, and a slit in the radial direction is providedthereon, so that the outer diameter of the spherical engaging section 84can elastically expand or contract. More specifically, by engaging apartial conical shaped convex surface that is formed on the head of anadjustment screw 86 that is screwed into the screw hole in the sphericalengaging section 84 with a partial conical shaped concave surface thatis formed in the opening section of the screw hole in the sphericalengaging section 84, it is possible to adjust the outer diameter of thespherical engaging section 84. By screwing the adjustment screw 86 aproper amount into the screw hole in the spherical engaging section 84,the occurrence of a gap in the spherical joint 83 is prevented. Withthis kind of construction, movement in the up-down direction istransmitted from the up-down feed nut 80 to the bottom-end section ofthe support frame 73 without looseness.

As illustrated in FIG. 7 and FIG. 9 reinforcement ribs 90 are providedon both the left and right sides of the front-end section of the vehiclebody-side bracket 32, and these reinforcement ribs 90 maintain thestrength and rigidity of the portion of the vehicle body-side bracketwhere the tilt shaft 33 is located. Moreover, reinforcement ribs 92 arealso provided between a pair of left and right pivot support arms 91that are provided on the front-end section of the column holder 31 inorder to pivotally support the column holder 31 by the tilt shaft 33 andthe main portion of the column holder 31, and these reinforcement ribs92 maintain the strength and rigidity of the pivot support arms 91.Therefore, in this example, the strength and rigidity of the pivotsupport section that supports the column holder 31 with respect to thevehicle body-side bracket 32 are sufficiently maintained, and theoperational feeling of the steering wheel 1 is sufficiently preventedfrom becoming deteriorated due to insufficient rigidity of this pivotsupport section.

In the following, the position adjustment of the steering wheel 1 by theelectric steering wheel position adjustment apparatus of this examplewill be explained. First, when adjusting the forward-backward positionof the steering wheel 1, current is allowed to flow to theforward-backward electric drive motor 56, and the forward-backwardelectric drive motor 56 rotates the forward-backward feed screw rod 58by a specified amount in a specified direction. With rotation of theforward-backward feed screw rod 58, the moving piece 16 a moves in theforward-backward direction along the forward-backward feed screw rod 58,and the steering column 5 b, by way of the transmission member 17 a, ismoved in the forward-backward direction inside the column holder 31. Asa result, the forward-backward position of the steering wheel 1 isadjusted. When the steering wheel 1 is moved to an adjustable limitposition, the moving piece 16 a comes in contact with one of a pair ofstoppers 87 a, 87 b as illustrated in FIG. 16 that are provided atportions near both ends of the forward-backward feed screw rod 58, andthe moving piece 16 a is prevented from moving any further. In thisstate, current flowing to the forward-backward electric drive motor 56is stopped.

When the forward-backward position of the steering wheel 1 is adjustedto a limit position, the portion on the end section in the axialdirection of the steering column 5 b where the outer ring 43 a, 43 b ofthe ball bearing 42 a, 42 b is fastened inside with an interference fitcomes close to the inner circumferential surface of the end section ofthe column holder 31. There is a possibility that the end sections inthe axial direction of the steering column 5 b may deform a little dueto the outer rings 43 a, 43 b being fastened inside, or due to theeffect of chucking during processing. However, the end sections in theaxial direction of the steering column 5 b are the reduced-diametersections 39 a, 39 b, and there is no rubbing between the end sections inthe axial direction of the steering column 5 b and the innercircumferential surface of the end sections of the column holder 31.Therefore, even when the forward-backward position of the steering wheel1 is adjusted to a limit position, unpleasant noise or vibration doesnot occur due to rubbing between the end section in the axial directionof the steering column 5 b and the inner circumferential surface of theend section of the column holder 31.

Next, when adjusting the up-down position of the steering wheel 1,current is allowed to flow to the up-down electric drive motor 57, andthe up-down electric drive motor 57 rotates the up-down feed screw rod78 by a specified amount in a specified direction. As a result, theup-down feed nut 80 moves in the up-down direction along the up-downfeed screw rod 78. However, this up-down feed nut 80 does not move inthe up-down direction due to engagement between the engaging hole 77 andthe spherical engaging section 84, so the up-down feed screw rod 78 isdisplaced in the up-down direction, and due to that displacement, theactuator case 53 and column holder 31 that support the up-down feedscrew rod 78 is pivotally displaced around the tilt shaft 33. As aresult, the up-down position of the steering wheel 1 is adjusted to aspecified position. In this case as well, when the steering wheel 1 ismoved to a limit position within the adjustable range, the up-down feednut 80 comes in contact with one of a pair of stoppers 88 a, 88 b suchas illustrated in FIG. 17 that are provided in portions near both endsof the up-down feed screw rod 78, and is prevented from furthermovement. In this state, electric current flowing to the up-downelectric drive motor 57 is stopped.

In the electric steering wheel position adjustment apparatus of thisexample, the steering shaft 2 b and steering column 5 b are integratedsuch that when both are in at least the normal state, the full length isnot expanded or contracted, so the rigidity of the steering shaft 2 band steering column 5 b is sufficiently maintained. Therefore, it ispossible to suppress vibration of the steering wheel 1 and improve thesteering performance. Moreover, in this way, the steering shaft 29having single construction is located inside the non-divided steeringcolumn 5 b, so an area of fit that is a cause of looseness does notexist in the portion that constitutes the steering column apparatus.Consequently, the occurrence of looseness in the portion thatconstitutes the steering column apparatus is suppressed, so it ispossible to increase the resonant frequency of that portion. As aresult, it becomes possible to avoid resonance with traveling vibrationthat has a low resonant frequency, or engine vibration having largeamplitude.

Moreover, the pair of sliding plates 35 that are supported in series attwo locations at the front and rear of the column holder 31 and thatsupport the steering column 5 b so as to be able to be displaced in theaxial direction elastically push the middle cylindrical section 40 ofthe steering column 5 b toward the inner circumferential surface of thecolumn holder 31, so looseness between the steering column 5 b and thecolumn holder 31 is eliminated. Particularly, by bringing the outercircumferential surface of the middle cylindrical section 40 having arelatively large diameter in contact with the sliding plates 35, thearea of the contact surface between these members becomes large, so itbecomes possible to make the force by which the sliding plates 35 pushthe steering column 5 b relatively small. Moreover, the gap in the axialdirection in the portion where the sliding plates 35 push the outercircumferential surface of the steering column 5 b can be kept as largeas possible within the range of movement in the forward-backwarddirection of the steering column 5 b, so the rigidity in the area of fitbetween the steering column 5 b and the column holder 31 is sufficientlymaintained. Furthermore, by using the moment that occurs between thesliding plates 35 and the sliding section on the outer circumferentialsurface of the steering column 5 b, it is possible to make the force bywhich the sliding plates 35 pushes the steering column 5 b relativelysmall. With this kind of construction, it is possible to reduce the loadthat is applied when moving the steering wheel 1 in the forward-backwarddirection, so it is possible to lessen the operating noise of theforward-backward electric drive motor 56. Moreover, even when thetolerance for the inner-diameter dimension of the column holder 31 andthe tolerance for the outer-diameter dimension of the steering column 5b are the same as in the conventional construction, it is possible toeliminate looseness, so tilting of the steering column 5 b and thetransmission member 17 a can be kept small. Therefore, there is no needto use a spherical shape having a high degree of displacement absorbencyfor the tip-end section of the transmission member 17 a, and it ispossible to use a simple shape such as a circular column shape.

In the apparatus of this example, construction does not allow expansionand contraction of the overall length of the steering shaft 2 b andsteering column 5 b, so when adjusting the forward-backward position ofthe steering wheel 1, the center position of the universal joint 27 a,and the joint cross 34, which is the center of displacement of theuniversal joint 27 a, is displaced in the axial direction of thesteering shaft 2 b and steering column 5 b. On the other hand, whenadjusting the forward-backward position of the steering wheel 1, theinstallation position of the tilt shaft 33 that is provided between thefront-end section of the column holder 31 and the front-end section ofthe vehicle body-side bracket 32 does not change even though theforward-backward position of the steering wheel 1 is adjusted.

Therefore, depending on the forward-backward position of the steeringwheel 1, a state occurs in which the center position of the joint cross34 is not located on the center axis of the tilt shaft 33. In thisstate, when pivotally displacing the column holder 31 centered aroundthe tilt shaft 33 in order to adjust the up-down position of thesteering wheel 1, the center position of the joint cross 34 is pivotallydisplaced centered around the tilt shaft 33. As the center of this jointcross 34 is pivotally displaced, the distance between the universaljoint 27 a on the rear side that includes this joint cross 34 and theuniversal joint on the front side changes. The change in this distanceis absorbed by the expansion or contraction of the intermediate shaft28. However, in order to expand or contract the intermediate shaft 28,it is necessary to overcome the friction resistance that acts in thearea of fit between the intermediate inner shaft 29 and the intermediateouter shaft 30. Due to this kind of friction resistance, the resistanceagainst the pivotal displacement of the column holder 31 becomes large,and there is a possibility that the capability for smooth adjustment ofthe up-down position of the steering wheel 1 will be lost. The amountthat this capability for smooth adjustment is lost becomes more extremeas the amount that the intermediate shaft expands or contracts duringadjustment of the up-down position becomes larger, and the resistancethat accompanies the expansion or contraction of the intermediate shaft28 becomes larger.

In the construction of this example, the center axis O_(C) of the tiltshaft 33 is located in the center position in the forward-backwarddirection between the center position O_(F) of displacement of thefront-end side and the center position O_(B) of displacement of therear-end side. Therefore, even in a state in which the center positionof the joint cross 34 is not located on the center axis O_(C) of thetilt shaft 33, it is possible to keep the radius of the pivotaldisplacement of the center position of the joint cross 34, accompanyingthe pivotal displacement of the column holder 31 centered around thetilt shaft 33, which is the amount that the center position of the jointcross 34 is shifted from the center axis O_(C), small. By keeping thisradius small, it is possible to keep the amount of expansion orcontraction of the intermediate shaft 28 due to adjustment of theup-down position small, and it is possible to keep the resistance due tothe expansion or contraction of the intermediate shaft 28 small. As aresult, it is possible to smoothly adjust the up-down position of thesteering wheel 1 regardless of the forward-backward position of thesteering wheel 1.

In FIG. 18, the positions represented by F, C and B indicate theposition of the center of displacement of the universal joint 27 a whenthe steering wheel 1 is moved to the front-end position, and the centerposition and rear-end position of the adjustable range when the up-downposition of the steering wheel 1 is in the neutral state. When theforward-backward position of the steering wheel 1 is in the centerposition, and the position of the center of displacement of theuniversal joint 27 a is located on the center axis of the tilt shaft 33,the universal joint 27 a does not raise or lower even when theintermediate shaft 28 expands or contracts as the up-down position ofthe steering wheel 1 is adjusted. Therefore, the intermediate shaft 28and universal joint 27 a do not resist the adjustment of the up-downposition of the steering wheel 1.

On the other hand, when adjusting the up-down position in a state inwhich the steering wheel 1 has been moved to the front-end positionrepresented by F the position of the center of displacement of theuniversal joint 27 a is displaced between f_(H) and f_(L) with f_(O) asthe center, and the intermediate shaft 28 expands or contracts due tothis displacement. As can be seen from FIG. 18, the amount of expansionor contraction between f_(H) and f_(L) is relatively large. This amountof expansion or contraction increases the longer the distance that theposition of the center of displacement of the universal joint 27 a isseparated from the tilt shaft 33 becomes. In the construction of thisexample, by locating the position of the center axis O_(C) of the tiltshaft 33 at the center position in the forward-backward directionbetween the position of the center of displacement O_(F) of thefront-end side and the position of the center of displacement. Os of therear-end side, it is possible to suppress the maximum value of thedistance that the position of the center of displacement of theuniversal joint 27 a is separated from the tilt shaft 33 more than inthe case of construction in which the center axis O_(C) is locatedfurther toward the rear than the position of the center of displacementO_(B) of the rear-end side. Therefore, even when adjusting the up-downposition when the steering wheel 1 is moved to the very front position,it is possible to keep this amount of expansion or contraction small andit is possible to perform the up-down position adjustment smoothly.

On the other hand, in a state in which the steering wheel 1 has beenmoved to the rear-end position represented by B, the universal joint 27a that connects the front-end section of the steering shaft 2 b and therear-end section of the intermediate shaft 28 is located further towardthe rear than the tilt shaft 33. When up-down position adjustment isperformed in this state, the position of the center of displacement ofthe universal joint 27 a is displaced between b_(H) and b_(L) with b_(O)as the center; and the intermediate shaft 18 expands or contracts due tothis displacement. As can be seen from FIG. 18, the amount of thisexpansion or contraction is kept relatively small. Instead of that,during up-down position adjustment of the steering wheel 1, the portionthat includes the universal joint 27 a becomes the load on the up-downelectric drive motor 57 of the electric actuator for up-down positionadjustment. This is because, unlike in the case when the universal joint27 a is located further toward the front than the tilt shaft 33, theweight of the portion of the universal joint 27 a is not cancelled outby other portions. Therefore, the load on the up-down electric drivemotor 57 during up-down position adjustment of the steering wheel 1becomes large, so a larger motor must be used, which is disadvantageousfrom the aspect of making the electric steering wheel positionadjustment apparatus more compact and lightweight. This tendency becomeseven more extreme the larger the distance that the universal joint 27 ais separated from the tilt shaft 33 becomes. However, in this example,the positional relationship of the center axis O_(C) of the tilt shaft33, and the positions of the center of displacement OF, O_(B) areregulated as described above, so when compared with construction inwhich the center axis O_(C) is located further toward the front than theposition of the center of displacement O_(F) on the front side, it ispossible to suppress the maximum value of the distance that the positionof the center of displacement of the universal joint 27 a is separatedfrom the tilt shaft 33. Therefore, it is possible to keep the amountthat the load on the up-down electric drive motor 57 becomes increaseslow, and thus it is easier to make the apparatus more compact andlightweight.

Locating the center axis O_(C) of the tilt shaft 33 at the centerposition in the forward-backward direction is also advantageous from theaspect of suppressing fluctuation in the torque required for operatingthe steering wheel 1, regardless of the adjustment of theforward-backward position of the steering wheel 1. In other words, whenthe universal joints 27 a, 27 b, which are both joint cross universaljoint, transmit torque in a state in which a joint angle is applied, thetorque characteristic (torque loss) changes in accordance with the phasevariation in the rotational direction. When this kind of change in thetorque characteristic is left as is, the driver that is operating thesteering wheel 1 will experience an unpleasant feeling. Therefore, bymaking the phase in the rotational direction of the universal joints 27a, 27 b suitably different, the fluctuations in torque characteristic ofthese universal joints 27 a, 27 b will cancel each other out. In thiscase, it is necessary to make suitable the relationship between thejoint angles of the universal joints 27 a, 27 b and the shift in thephase in the rotational direction, however, in the construction of thisexample, the position of the universal joint 27 a on the rear sideshifts as the forward-backward position of the steering wheel 1 isadjusted. As a result, the relationship of the joint angles of theuniversal joints 27 a, 27 b shifts from the initial relationship. Whenthis shift is large, it is not possible to sufficiently suppress thefluctuation in the torque characteristic of these universal joints 27 a,27 b, and there is a possibility that the driver that is operating thesteering wheel 1 will experience an unpleasant feeling. On the otherhand, in the construction of this example, it is possible to keep theamount of this shifting small, so it is possible to keep the possibilitythat driver that is operating the steering wheel 1 will experience anunpleasant feeling low.

Moreover, the sliding plates 35 push the steering column 5 b downwardtoward the forward-backward feed screw apparatus 54, so a moment in thehorizontal direction does not occur according to this pushing, andlooseness of the steering column 5 b inside the column holder 31 thatmay occur when the forward-backward feed screw apparatus 54 is operatedand stopped is suppressed, and up-down movement of the steering column 5b that may occur when inverting the displacement operation is alsosuppressed. Even in the case where it is necessary to perform afinishing process on the outer circumferential surface of the middlecylindrical section 40 in order to improve the precision of the area offit between the outer circumferential surface of the steering column 5 band the inner circumferential surface of the column holder 31, the outercircumferential surface of the middle cylindrical section 40 has thelargest diameter of the outer circumferential surface of the steeringcolumn 5 b, so performing a finishing process on the outercircumferential surface of this middle cylindrical section 40 does noteffect the other portions, and can be performed easily and efficiently.Moreover, the support rigidity of the steering wheel 1 as well can beeasily adjusted by changing the thickness of the metal plate of thesteering column 5 b and steering shaft. 2 b. Furthermore, the portionsof the steering column 5 b that are pushed by the sliding plates 35 arelocated in the portion of the steering column 5 b having the largerdiameter, so the surface area of the pushed portions can be made large,and thus it is not necessary to make the force by which the slidingplates 35 push the steering column 5 b excessively large. The effect ofsuppressing looseness is obtained by a small pushing force such as this,so the load during operation is stable and small and thus it is alsopossible to reduce the operating noise of the forward-backward electricdrive motor 56.

In the construction of this example, the shape of the transmissionmember 17 a and the cylindrical spacer 72 for transmitting the movementof the moving piece 16 a of the forward-backward feed screw apparatus 54to the steering column 5 b is simple, so it is possible to use coldforging to manufacture the transmission member 17 a and cylindricalspacer 72 at low cost and with high precision.

Moreover, the relative displacement in the axial direction of thetransmission member 17 a between the transmission member 17 a and themoving piece 16 a is compensated for at two locations; the innercircumferential surface and outer circumferential surface of thecylindrical spacer 72, and the outer circumferential surface of thetip-end section of the transmission member 17 a and the innercircumferential surface of the engaging concave section 19 a that isprovided on the moving piece 16 a. Therefore, even when the direction ofmovement of the moving piece 16 a and the direction of movement of thesteering column 5 b accompanying adjustment of the forward-backwardposition of the steering wheel 1 become nonparallel due to bad precisionof the engaging bottom surface of the column holder 31 and the topsurface of the actuator case 53, and there is relative displacement inthe axial direction of the transmission member 17 a between thetransmission member 17 a and the moving piece 16 a accompanying theforward-backward position adjustment of the steering wheel 1, there isrubbing at two locations, so the length of each rubbing location can bemade short, and thus it is possible to suppress the occurrence of noiseand vibration. Furthermore, there is no neck section in the transmissionmember 17 a, that is disadvantageous from the aspect of maintainingstrength and rigidity, so the durability and reliability of theforward-backward feed screw apparatus 54 is maintained.

Furthermore, with construction of this example, the up-down feed screwrod 78 of the up-down feed screw apparatus 55 is located directly belowthe column holder 31 in the radial direction of the column holder 31, sono adverse moment is applied to the column holder 31 during up-downposition adjustment of the steering wheel 1. Therefore, it is possibleto perform this up-down position adjustment smoothly. Locating thesupport frame 73 for guidance during up-down position adjustment as fartoward the rear as possible within a range that does not interfere withthe portion fastened to the steering column 5 b is preferred from theaspect of maintaining support rigidity of the column holder 31 as wellas maintaining the support rigidity of the steering wheel 1 regardlessof the forward-backward movement of the steering column 5 b duringforward-backward position adjustment of the steering wheel 1. Moreover,preferably the sliding plates 75 a, 75 b are coated with a lubricantsuch as grease in order that up-down adjustment of the steering wheel 1is performed smoothly. Furthermore, preferably arranging the up-downfeed screw rod 78 and the forward-backward feed screw rod 58 such thatthe center axes are orthogonal to each other is preferred from theaspect of being able to smoothly perform up-down adjustment andforward-backward adjustment of the steering wheel 1, and being able tokeep the installation space of the forward-backward feed screw apparatus54 and up-down feed screw apparatus 55 small.

Second Example of an Embodiment

FIG. 19 and FIG. 20 illustrate a second example of an embodiment of thepresent invention. This example illustrates the case in which theconstruction of the present invention is applied to the second exampleof conventional technology: In this example, the steering shaft 2 a hasa cylindrical outer shaft 3 a, and a circular rod shaped inner shaft 4 athat is inserted inside the outer shaft 3 a so as to be able to slide inthe axial direction and be able to transmit torque. Moreover, thesteering column 5 c of the column unit of the present invention has acylindrical outer column 6 c that is supported by an installationbracket 14, and a cylindrical inner column 7 c that is inserted insidethe outer column 6 c so as to be able to slide in the axial direction.The steering shaft 2 a is supported on the inside of the steering column5 c so as to be able to rotate freely, and the outer shaft 3 a and theinner column 7 c move in the forward-backward direction relative to theinner shaft 4 a and the outer column 6 c. In this example, the outercolumn 6 c corresponds to the support section of the column unit of thepresent invention, and the inner column 7 c corresponds to the adjustedsection of the column unit of the present invention.

As illustrated in FIG. 19, in this example, in order to eliminatelooseness of the inner column 7 c with respect to the outer column 6 c,holding holes 22 b are formed at two locations in the top surface of theouter column 6 c that are separated in the forward-backward direction soas to pass through between the inner circumferential surface and outercircumferential surface of the outer column 6 c. Inside each of theholding holes 22 b, there is assembled in order from the inside asliding plate 35, a washer 36, and a disc spring 37, and the opening onthe top end of the holding hole 22 b is covered by a screw cover 38. Inthis state, the sliding plates 35 located on the radially inward sideends of the holding holes are pushed against the outer circumferentialsurface (top surface) of the inner column 7 c by the elastic force ofthe disc springs 37.

In this example, a linear motion ultrasonic motor 15 a that is supportedby the bottom-end section of the installation bracket 14 causes theinner column 7 c to be displaced in the axial direction with respect tothe outer column 6 c. A moving piece 16 b that is provided in the linearmotion ultrasonic motor 15 a and arranged so as to be able to move inthe axial direction (forward-backward) direction of the steering column5 c has a base section that is connected to the linear motion ultrasonicmotor 15 a and a connecting section 61 a that is provided above the basesection 6 a, and an engaging concave section 19 b is provided in thecenter section of this connecting section 61 a.

In this example as well, the transmission member 17 a has a male screwsection 63 on the top-end section thereof, an outward facing flangesection 64 around the middle section, and a circular column section 65on the bottom-end section. The transmission member 17 a is fastened byscrews to the inner column 7 c in a state such that filler pieces 71 areheld between the top surfaces of a radially inward side spacer 69 and aradially outward side spacer 70 that are arranged around the top surfaceof the flange section 64 and the inner column 7 b. The circular columnsection of the transmission member 17 a is placed inside the engagingconcave section 19 b of the moving piece 16 b by way of a cylindricalshaped spacer 72 so as to be able to slide in the axial direction of thetransmission member 17 a without looseness.

The engaging concave section 19 b of the moving piece 16 b has an innercircumferential surface that is a cylindrical concave surface having aninner diameter that does not change in the axial direction of thetransmission member 17 a; the circular column section 65, which is thetip-end section of the transmission member 17 a, has an outercircumferential surface that is a cylindrical convex surface having anouter diameter that does not change in the axial direction of thetransmission member 17 a; and the cylindrical shaped spacer 72 has anouter circumferential surface that is a cylindrical convex surfacehaving an outer diameter that does not change in the axial direction ofthe transmission member 17 a and an inner circumferential surface thatis a cylindrical concave surface having an inner diameter that does notchange in the axial direction of the transmission member 17 a. The otherconstruction and functions of this example are the same as in the firstexample of an embodiment.

INDUSTRIAL APPLICABILITY

The electric steering wheel position adjustment apparatus of the presentinvention can be applied to not only to the adjustment of theforward-backward position of a steering wheel as described in theembodiment above, but can also be suitably applied to an electric tiltand telescopic steering apparatus that is able to adjust the up-downposition of the steering wheel as well. The invention can also beapplied to an electric telescopic steering apparatus that does not havea tilt mechanism and that adjusts only the forward-backward position ofthe steering wheel. Moreover, the construction for attachment to avehicle body, and construction for joining the steering shaft anduniversal joint are not limited, and the present invention can be widelyapplied to electric steering wheel position adjustment apparatuses thatare assembled in electric steering apparatuses in which various kinds ofconventionally known construction are employed.

EXPLANATION OF REFERENCE NUMBERS

-   1 Steering wheel-   2, 2 a, 2 b Steering shaft-   3, 3 a Outer shaft-   4, 4 a Inner shaft-   5, 5 a, 5 b, 5 c Steering column-   6, 6 a, 6 b, 6 c Outer column-   7, 7 a, 7 b, 7 c Inner column-   8 Gear housing-   9 Feed nut-   10 Push-pull arm-   11 Push-pull rod-   12 Male screw section-   13 Worm reducer-   14 Installation bracket-   15, 15 a Linear motion ultrasonic motor-   16, 16 b Moving piece-   16 a Moving piece (forward-backward feed nut)-   17, 17 a Transmission member-   18 Spherical joint-   19, 19 a, 19 b Engaging concave section-   20 Spacer-   21 Spherical engaging section-   22, 22 a, 22 b Holding hole-   23 Female screw-   24 Adjustment screw-   25 Disc spring-   26 Pad-   27 a, 27 b Universal joint-   28 Intermediate shaft-   29 Intermediate inner shaft-   30 Intermediate outer shaft-   31 Column holder-   32 Vehicle body-side bracket-   33 Tilt shaft.-   34 Joint cross-   35 Sliding plate-   36 Washer-   37 Disc spring-   38 Screw cover-   39 a, 39 b Reduced-diameter section-   40 Middle cylindrical section-   41 a, 41 b Inclined surface section-   42 a, 42 b Ball bearing-   43 a, 43 b Outer ring-   44 a, 44 b Inner ring-   45 Retaining ring-   46 Push nut-   47 Elastic material-   48 Screw hole-   49 Installation plate section-   50 Long hole-   51 Notch-   52 a, 52 b Sliding plate-   53 Actuator case-   54 Forward-backward feed screw apparatus-   55 Up-down feed screw apparatus-   56 Forward-backward electric drive motor-   57 Up-down electric drive motor-   58 Forward-backward feed screw rod-   59 a, 59 b Ball bearing-   60, 60 a Base section-   61, 61 a Connecting section-   62 Screw hole-   63 Male screw section-   64 Flange section-   65 Circular column section-   66 Fastening hole-   67 Through hole-   68 Nut plate-   69 Radially inward side spacer-   70 Radially outward side spacer-   71 Filler piece-   72 Cylindrical spacer-   73 Support frame-   74 a, 74 b Convex section-   75 a, 75 b Sliding plate-   76 Pressure screw-   77 Engaging hole-   78 Up-down feed screw rod-   79 a, 79 b Ball bearing-   80 Up-down feed nut-   81 Screw-   82 Engaging arm-   83 Spherical joint-   84 Spherical engaging section-   86 Spacer-   87 a, 87 b Stopper-   88 a, 88 b Stopper-   89 Long hole in the forward-backward direction-   90 Reinforcement rib-   91 Pivot support arm-   92 Reinforcement rib

1. An electric steering wheel position adjustment apparatus, comprising:a steering shaft having a rear-end section which a steering wheel issupported by and fastened to; and a column unit extending in an axialdirection of the steering shaft and rotatably supporting the steeringshaft on an inside of the column unit, the column unit comprising: asupport section supported by a portion that is fastened to a vehiclebody or to a vehicle body-side bracket that is supported by the portionthat is fastened to the vehicle body, the support section not beingdisplaced during position adjustment of the steering wheel; and anadjusted section supported by the support section so as to bedisplaceable in the axial direction of the steering shaft together withat least part of the steering shaft during position adjustment of thesteering wheel; an electric actuator fastened to a bottom side of thesupport section, and having an electric motor as a drive source, causingthe adjusted section to be displaced in the axial direction of thesteering shaft with respect to the support section; mechanisms pushingthe adjusted section downward, the mechanisms being provided in at leasttwo locations on a top side of the support section that are separated ina forward-backward direction of the column unit, and a pair of preloadedangular ball bearings having back-to-back contact angles and beinglocated between both end sections in the forward-backward direction ofthe adjusted section and at least part of the steering shaft, and thepair of ball bearings rotatably supporting the at least part of thesteering shaft with respect to the adjusted section in a state thatdisplacement in the axial direction of the steering shaft with respectto the adjusted section is prevented.
 2. (canceled)
 3. The electricsteering wheel position adjustment apparatus according to claim 1,wherein the both end sections in the forward-backward direction of theadjusted section are constructed by reduced-diameter sections havingdiameters that are smaller than a diameter of a middle section in theforward-backward direction of the adjusted section, the middle sectionin the forward-backward direction of the adjusted section is constructedby a middle cylindrical section having an outer diameter that does notchange in the axial direction, the pair of ball bearings are locatedbetween inner circumferential surfaces of the both end sections in theforward-backward direction of the adjusted section and an outercircumferential surface of the at least part of the steering shaft, andthe mechanisms pushing the adjusted section downward are provided so asnot to separate from the middle cylindrical section regardless ofdisplacement in the axial direction of the adjusted section with respectto the support section.
 4. The electric steering wheel positionadjustment apparatus according to claim 1, wherein each of themechanisms pushing the adjusted section downward comprises: a holdinghole formed so as to pass through between an inner circumferentialsurface and an outer circumferential surface of the support section; asliding plate; an elastic member; and a cover, the sliding plate, theelastic member and the cover being assembled in the holding hole inorder from an inside in a radial direction of the support section, andthe elastic member is elastically compressed between the sliding plateand the cover, such that the sliding plate pushes an outercircumferential surface of the adjusted section.
 5. The electricsteering wheel position adjustment apparatus according to claim 1,wherein spacing in the axial direction of the mechanisms pushing theadjusted section downward is essentially equal to a maximum range ofmovement of the adjusted section in the axial direction of the supportsection.
 6. The electric steering wheel position adjustment apparatusaccording to claim 3, wherein the electric actuator comprises: aforward-backward feed screw rod being arranged parallel with theadjusted section, and being rotated and driven by the electric motor, amoving piece being screwed onto the forward-backward feed screw rod, andmoving in the forward-backward direction according to rotation of theforward-backward feed screw rod; and a transmission member having atip-end section that is connected to the moving piece and a base-endsection that is joined to the middle cylindrical section of the adjustedsection, and transmitting movement of the moving piece to the adjustedsection.
 7. The electric steering wheel position adjustment apparatusaccording to claim 6, wherein an engaging concave section is provided inthe moving piece, the tip-end section of the transmission member engageswith the engaging concave section of the moving piece by way of aspacer, the engaging concave section of the moving piece has an innercircumferential surface that is a cylindrical concave surface having aninner diameter that does not change in an axial direction of thetransmission member, the tip-end section of the transmission member hasan outer circumferential surface that is a cylindrical convex surfacehaving an outer diameter that does not change in the axial direction ofthe transmission member, and the spacer has an outer circumferentialsurface that is a cylindrical convex surface having an outer diameterthat does not change in the axial direction of the transmission memberand an inner circumferential surface that is a cylindrical concavesurface having an inner diameter that does not change in the axialdirection of the transmission member.
 8. The electric steering wheelposition adjustment apparatus according to claim 1, wherein the steeringshaft has integrated construction of which an overall length thereofdoes not expand or contract, and the adjusted section comprises asteering column having integrated construction of which an overalllength thereof does not expand or contract, wherein the electricsteering wheel position adjustment apparatus further comprises: anexpandable intermediate shaft transmitting rotation of the steeringshaft to an input shaft of a steering gear unit; and a universal jointconnecting a front-end section of the steering shaft and a rear-endsection of the intermediate shaft, wherein the electric actuator causesthe steering column to be displaced in the axial direction of thesteering column, causing the steering shaft to move in theforward-backward direction, and movement of the steering shaft iscompensated by causing the intermediate shaft to expand or contract.